Circuit for frequency transformation of high-frequency oscillations



Dec. 25, 1956 J. H. JONKER ETAL 2,775,690

cmcurr FOR FREQUENCY TRANSFORMATION OF HIGH-FREQUENCY OSCILLATIONS FiledFeb. 26, 1952 2 Sheets-Sheet 1 at A? T INVENTO'RS Gesinus Diemer JohanLodewijk Hendrik Jonk r Dec. 25, 1956 J. L. H. JONKER ET AL 2,775,690

cmcun FOR FREQUENCY TRANSFORMATION OF HIGH-FREQUENCY OSCILLATIONS FiledFeb. 26, 1952 2 Sheets-Sheet 2 INVENTORS Gesinus Diemer Johan Lode ijkHendrik onker By M Agent United States Patent CIRCUIT FOR FREQUENCYTRANSFORMATIGN OF HIGH-FREQUENCY OSCILLATIONS Johan Lodewiik HendrikJonker and Gesinus Biemer,

Eindhoven, Netherlands, assignors to Hartford National Bank and TrustCompany, Hartford, Conn., as trustee Application February 26, 1952,Serial No. 273,435

Claims priority, application Netherlands March 5, 1951 Claims. c1.2s0-z0 The present invention relates to a circuit arrangement forfrequency transformation of high frequency oscillations.

In order to provide frequency transformation of the signal oscillationsreceived by superheterodyne receivers it has been suggested to use amixer in which an electron beam issuing from the cathode isintensity-controlled by a control electrode to which a firsthigh-frequency voltage is applied. A second high-frequency voltage issupplied to two deflecting electrodes, which are arranged symmetricallyabout the normal axis of the beam (the axis of the beam in the absenceof control voltages) to deflect said beam. The electrons of .the beamthen strike an anode system comprising two parts, which are alsoarranged symmetrically about the normal beam axis and which haveconnected bet-ween them an output circuit which yields the intermediatefrequency oscillation. Each of the parts of the anode system is thusstruck by a greater or lesser part of the electron current in accordancewith the extent of deflection.

In such a circuit arrangement the electron current may beintensity-controlled by oscillations from a local oscillator anddeflection-controlled by a received signal. As an alternative, thereverse is possible. In the latter case, there is no electrostaticinduction effect of the oscillator voltage on the control grid, andelectrons, after being deflection-controlled, cannot return to thecontrol grid. Local-oscillator frequency energy is consequentlysubstantially not radiated from the receiver antenna. In such circuitarrangements a separate local-oscillator is generally used.

It has also been suggested that with a mixer circuit comprising adischarge tube in which an electron beam is first intensity-controlledby the signal oscillation and then deflection-controlled by alocal-oscillator oscillation, the local-oscillations should be producedin the tube itself by returning the electrons to the deflectingelectrodes with the use of a hollow reflection-anode, a circuit tuned tothe oscillator frequency being connected between one of the deflectingelectrodes and a point of constant potential and oscillations being setup in this circuit due to the negative resistance produced between thesaid electrode and ground. The output circuit in which the differencefrequency or the sum frequency oscillations are produced is connectedbetween the other deflecting electrode and ground. However, in thiscircuit the deflection control is asymmetrical with respect to ground,since the deflecting electrodes and ground have connected between themcircuits which are tuned to different frequencies.

The object of the invention is to provide a circuit for frequencytransformation of high-frequency electrical oscillations (i530 mc./s.)comprising a discharge tube which acts as a mixing tube. The cathode ofthe discharge tube emits an electron beam which is intensity-controlledby a control electrode to which .a first high-frequency voltage isapplied. This beam under the action of two deflecting electrodesarranged symmetrically of the normal axis of the electron beam andhaving a second highfrequency voltage applied to them, is subjected todeflection-control.

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The electrons of the beam then strike an anode system constituted by twoparts which are arranged symmetrically of the normal beam axis and whichmay be the deflecting electrodes themselves. Said parts have theintermediate frequency output circuit connected between them and areeach struck by a larger or smaller portion of the electrons of the beamin accordance with the extent of deflection. The circuit is constructedin a manner such that the tube is self-oscillating while at the sametime the beam is deflection-controlled wholly symmetrically. The presentinvention is based on recognition of the fact that with a symmetricalcircuit it is possible both for the circuit in which the oscillatoroscillations are produced and for that in which the intermediatefrequency oscillations occur to be connected between the two parts ofthe anode system, without one circuit being a short-circuit for theother.

In accordance with the present invention, the parts of the anode systemand the deflecting electrodes are coupled together crosswise so that theecond high-frequency voltage is produced by the negative resistance thusproduced between the two said parts in the tube itself and a circuitdetermining the frequency of the resultant oscillation is also connectedbetween the parts of the anode system so that the said circuits aresymmetrical with respect to ground.-

Both the intermediate frequency circuit and the local- .oscillatorcircuit are symmetrical with respect to ground,

it being possible to connect between the parts of the anode system animpedance of which the mid-point is grounded so far as high-frequencyoscillations are conecemed, and of which a part arranged symmetricallyof the mid-point is shunted by a capacitor which together with this partconstitutes a circuit tuned to the intermediate frequency, whereas theremaining part of the impedance, together with a capacity availablebetween the parts of the anode system, preferably the natural capacitybetween these parts, constitutes a circuit tuned to the oscillatorfrequency, the circuit tuned to the intermediate frequency being ashort-circuit for the oscillator oscillations, since the frequency ofthe latter is much higher than the intermediate frequency.

In addition, it is possible for an inductor connected between the partsof the anode system, and the mid-point of which is grounded forhigh-frequency oscillations, to be provided with two taps arrangedsymmetrically of the mid-point. It is also possible to connectcapacitors of equal capacity which tune the inductor to the intermediatefrequency, between each of these taps and the ends of the inductor, thecentral part of the inductor forming with the capacity available betweenthe parts of the anode a circuit tuned to the oscillator frequency.

It willbe noted that it is known to produce oscillations by means of atube having an electron beam and comprising two deflecting electrodesand two anodes by interconnecting the deflecting electrodes and theanodes crosswise. In this case, frequency transformation does not occur.It is also known to produce the oscillator oscillation in the mixingtube itself, for example, by using the first two grids as oscillatorelectrodes. This arrangement is not symmetrical with respect to groundas far as the oscillator oscillation is concerned.

In order that the invention may be more clearly understood and readilycarried into eifect, it .will now be described more fully with referenceto the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a preferred embodiment of the circuitarrangement of the present invention; Fig. 2 is a modification of theembodiment of Fig. 1;

Fig. 3 is a sectional view, taken at right angles to the cathode, of amixing tube preferably used in accordance with the circuit arrangementof the present invention;

Fig. 4 is a schematic diagram of another embodiment of the circuitarrangement of the present invention; and

Fig. is a schematic diagram of still another embodiment of the circuitarrangement of the present invention.

Referring to Fig. 1, an antenna circuit 1 is coupled inductively to aninput circuit 2 tuned to the signal frequency and connected between thecontrol grid 5 of a mixing tube 3 and ground. The tube includes, inaddition, a cathode 4, which is grounded through a grid bias network 18,19, a screen grid 6 which, as usual, has a positive voltage applied toit, two deflecting electrodes 7 and 7 and two anodes 8, 8'. Thearrangement is such that the cathode 4 emits an electron beam which mayotherwise have a comparatively large cross-sectional area. Thearrangement is symmetrical, so that in the absence of voltage betweenthe deflecting electrodes 7 and 7' equal portions of the electrons ofthe beam pass to the anodes 8 and 8'.

In order to produce the oscillator oscillation in the tube itself thedeflecting electrode 7 is connected to the anode 8' and the deflectingelectrode 7' is connected to the anode 8. This is effected by connectingleads which are as far as possible symmetrical with respect to thecentral plane of the beam. Thus a negative resistance is producedbetween the anodes. The interconnected electrode pairs have connectedbetween them an inductor 9 whose midpoint is connected to the positiveterminal of the supply source, the negative terminal of which isgrounded. Two points of the inductor 9 arranged symmetrically about themidpoint have connected between them a capacitor 10 which together withthe central part of the inductor 9 constitutes a circuit tuned to theintermediate frequency, from which the intermediate frequencyoscillations are derived by means of an inductor 12 which is coupledsymmetrically to the inductor 9. The oscillator voltage applied inpush-pull with respect to ground between the electrodes 7 and 8' on theone hand and 7 and 8 on the other, induces, even at very highfrequencies, substantially no voltage between the grid 5 and ground.

If, as usual, the difference between the oscillator frequency and thesignal frequency constitutes the intermediate frequency, the capacitor10 will have a comparatively high capacity and is short-circuit for theoscillations of oscillator frequency. The outer parts of the inductor 9together with the capacity 11, which is constituted, for example, by thenatural capacities between the anodes or the deflecting electrodesrespectively, constitute a circuit whose tuning determines theoscillator frequency produced.

In Fig. 2, the inductor 9 has connected between its taps and its ends,capacitors 13 and 14, having equal capacities such that a circuit tunedto the intermediate frequency is formed again between the anodes. Inthis case, the oscillator frequency is determined by the inductance ofthe central part and the natural capacities between the electrodesconnected to the inductor 9. The capacitors 13 and 14 are againshort-circuits for the oscillator frequency. The advantage of thiscircuit arrangement over that shown in Fig. 1 is that if tuning iseffected by variation of the inductors, the construction of the receiveris simplified.

Fig. 3 shows in greater detail a sectional view of a discharge tube ofthe kind preferably used with circuit arrangements according to theinvention, the section being taken normal to the cathode axis. Thecathode 4 is constructed so as to constitute a flat web emittingsubstantially from the broad sides so that two flat beams are emitted,the central plane of which passes through the cathode axis and is normalto the plane of the cathode. The stay rods 15 and 15 for the controlgrid 5 have some supplementary bunching effect on the electron currentas do the bunching rods 16, 16, 16" and 16" connected to the cathode.The beams emanating from the two sides of the cathode, after passing thescreen grid 6, reach the deflection-control spaces, one of which iscircumscribed by the deflecting electrodes 7, 7' and the anodes 8, 8 andthe other by the deflecting electrodes 7", 7" and the anodes 8", 8'.With the use of known screening means the capacity between each of theparts which are at the oscillator voltage and the parts which are at thesignal voltage is made as low as possible. The deflecting electrodes 7,7', 7", 7" are interconnected, similarly to the anodes 8, 8', 8", 8", byconductors which should be arranged, as far as possible symmetricallywith respect to the screening. The said interconnection may be direct orcapacitative. In the latter case, there is the advantage that the biasvoltage of the deflecting electrodes is enabled to be less than that ofthe anode. This permits the capacities between the sets ofinterconnected electrodes and the control grid to be perfectlyequalized. The rod-shaped electrodes 17 and 17' act to reduce the effectof the secondary emission on the anodes.

The invention is particularly useful for television and frequencymodulation receivers, since it has been extremely difficult to reducethe radiation of oscillator frequency from the receiving antenna so asnot to interfere with neighbouring receivers. It has been found that,particularly in the use of a tube construction as shown in Fig. 3, theuse of the invention permits the effective removal of such interference.

Fig. 4 shows an embodiment of the invention, in which the deflectingelectrodes also act as anodes, the tube 21 being again preferablyconstituted to comprise a flat cathode 4 which emits on two sides. Thecontrol grid 5, the screen grid 6, the bunching rods 16 and thedeflecting electrodes 7, 7, 7", 7" are formed and arranged in the samemanner as in the embodiment shown in Fig. 3, but the partite anodeconstruction shown in Figs. 1, 2 and 3 is replaced by hollow reflectionelectrodes 22 and 22', respectively, which have the same voltage as thecathode, or are slightly negative in relation to the cathode. Theelectrons which have passed the deflect ing electrodes are thrown backby the electrodes 22 and 22' in a manner such that if the deflectingelectrode 7 is positive in relation to the deflecting electrode 7' andin relation to ground, the greater part of the reflected electronsreaches the deflecting electrode 7 and vice versa. Thus a negativeresistance occurs between the deflecting electrodes 7, 7 and 7", 7",respectively, so that oscillations are produced in the oscillatorcircuit connected to these electrodes. In order to obtain a controlwhich is symmetrical as far as possible, the deflecting electrodes 7 to7" are interconnected crosswise. The remaining part of the circuit isconstructed in the same manner as in Fig. 1. The circuit arrangementshown in Fig. 4 also permits effective suppression of the oscillatoroscillation in the antenna circuit.

With the circuits described, it is possible to ground the control gridof the tube and to apply a high-frequency voltage relative to ground tothe cathode.

Fig. 5 shows a circuit of this kind in which the various elements aredesignated with the same reference numerals as the correspondingelements of Fig. 1. In this case there is no need for a screen grid. Theadvantage of this grid base circuit in the present case is that thedeflected beam is more sharply defined, because the smaller the numberof grids arranged in the beam, the less is the discrepancy in formedspeed of the electrons in the beam.

While the invention has been described by means of specific examples andin specific embodiments, we do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

What we claim is:

1. A circuit arrangement for mixing a high-frequency wave with a localoscillation to produce a beat voltage having a frequency other than thatof said local oscillation, said circuit arrangement comprising anelectron discharge tube provided with means including a cathode forgenerating an electron beam, an intensity control electrode for saidbeam, first and second deflection electrodes arranged symmetrically oneither side of the normal axis of said beam and first and second anodeelectrodes arranged symmetrically on either side of the normal axis ofthe beam whereby portions of said beam strike each anode, thedistribution of said beam between said first and second anode electrodesbeing determined by the extent of beam deflection, a first resonantcircuit coupled between said first and second anode electrodes and tunedto the frequency of said heat voltage, said first circuit havingsymmetrically interposed therein a second resonant circuit tuned to thefrequency of said local oscillation, means coupling the first and secondanode electrodes respectively to the second and first deflectionelectrodes, and means to apply said wave between said control electrodeand said cathode whereby said local oscillation is self-generated withinthe tube thereby producing said beat voltage across said first circuit.

2. A circuit arrangement as set forth in claim 1 further including meanscoupled to the mid-point of said first circuit to apply an operatingpotential relative to said cathode to both anode electrodes.

3. A circuit arrangement as set forth in claim 1 wherein said controlelectrode is grounded.

4. A circuit arrangement as set forth in claim 1 wherein said anode anddeflection electrodes are conductively coupled.

5. A circuit arrangement as set forth in claim 1 wherein said anode anddeflection electrodes are capacitively coupled.

6. A circuit arrangement for mixing a high-frequency wave with a localoscillation to produce a beat voltage having a frequency other than thatof said local oscillation, said circuit arrangement comprising anelectron discharge tube provided with means for generating an electronbeam, an intensity control electrode for said beam, first and seconddeflection electrodes arranged symmetrically on either side of thenormal axis of said beam and first and second anode electrodes arrangedsymmetrically on either side of the normal axis of the beam wherebyportions of said beam strike each anode, the distribution of said beambetween said first and second anode electrodes being determined by theextent of beam deflection, an inductance coupled between said first andsecond anode electrodes, said inductance together with the naturalcapacitance of said anode electrodes forming a first resonant circuittuned to the frequency of said local oscillation, the mid-point of saidinductance being grounded for high-frequencies, a capacitance connectedbetween two points on said inductance which are symmetric with respectto said mid-point, said capacitance together with that portion of theinductance included between said two points forming a second resonantcircuit tuned to the frequency of said beat voltage, means coupling thefirst and second anode electrodes respectively to the second and firstdeflection electrodes, and means to apply said wave to said controlelectrode whereby said local oscillation is self-generated within thetube thereby producing said beat voltage across said second circuit.

7. A circuit arrangement for mixing a high-frequency wave with a localoscillation to produce a beatvoltage having a frequency other than thatof said local oscillation, said circuit arrangement comprising anelectron discharge tube provided With means including a cathode forgenerating two electron beams, an intensity control electrode for eachbeam, first and second deflection electrodes for each beam arrangedsymmetrically on either side of the normal axis of said beam and firstand second anode electrodes for each beam arranged symmetrically oneither side of the normal axis of the beam whereby portions of said beamstrike each anode, the distribution of said beam between said first andsecond anode electrodes being determined by the extent of beamdeflection, a first resonant circuit coupled between said first andsecond anode electrodes and tuned to the frequency of said beat voltage,said first circuit having symmetrically interposed therein a secondresonant circuit tuned to the frequency of said local oscillation, meanscoupling the first and second anode electrodes respectively of each beamto the second and first deflection electrodes of said each beam, andmeans to apply said wave to said control electrode of each beam wherebysaid local oscillation is self-generated within the tube therebyproducing said beat voltage across said first circuit.

8. A circuit arrangement as set forth in claim 7 wherein said controlelectrodes are constituted by a common grid.

9. A circuit arrangement for mixing a high-frequency wave with a localoscillation to produce a beat voltage having a frequency other than thatof said local oscillation, said circuit arrangement comprising anelectron discharge tube provided with means for generating an electronbeam, an intensity control electrode for said beam, first and seconddeflection electrodes arranged symmetrically on either side of thenormal axis of said beam and first and second anode electrodes arrangedsymmetrically on either side of the normal axis of the beam wherebyportions of said beam strike each anode, the distribution of said beambetween said first and second anode electrodes being determined by theextent of beam deflection, an inductance coupled between said first andsecond anode electrodes and having a mid-point tap and two taps arrangedsymmetrically with respect to said midpoint tap, said mid-point tapbeing grounded for highfrequencies, two capacitances each of which iscoupled between one of said two taps and the adjacent end of theinductance to form a first circuit tuned to the frequency of said beatvoltage, the portion of said inductance included between said two tapstogether with the natural capacitance of said anode electrodesconstituting a second circuit tuned to the frequency of said localoscillation, means coupling the first and second anode electrodesrespectively to the second and first deflection electrodes, and means toapply said wave to said control electrode whereby said local oscillationis self-generated within the tube thereby producing said beat voltageacross said first circuit.

10. Apparatus for mixing a high-frequency wave with a local oscillationto produce a beat voltage having a frequency other than that of saidlocal oscillation, said apparatus comprising an electron discharge tubeincluding a cathode to generate an electron beam having a normal axis, acontrol electrode for modulating the intensity of the beam, and firstand second pairs of deflection and anode electrodes disposedsymmetrically about the normal axis, electrodes of each pair beingdisposed on opposite sides of said normal axis, circuit means connectingthe electrodes of said first andsecond pairs disposed on one side ofsaid beam axis to the electrodes of said second and first pairsrespectively disposed on the other side of said axis, a first resonantcircuit tuned to the frequency of said local oscillation and coupled tosaid circuit means to porduce the local oscillation in said tube andhaving a mid-point, said first resonant circuit including a secondresonant circuit symmetrically arranged about said midpoint and tuned tothe frequency of said heat voltage, and means to apply saidhigh-frequency wave between said cathode and said control electrodewhereby said highfrequency wave is mixed in said tube with said localoscillation to produce said heat voltage across said second circuit.

References Cited in the file of this patent UNITED STATES PATENTS1,988,621 Hansell Ian. 22, 1935 2,042,321 Lindenblad May 26, 19362,504,626 Bell Apr. 18, 1950 2,564,063 Herold Aug. 14, 1951

